Means for reproducing sound from graphical records



0a. 27, 1925. I 1,558,673 R. HART MEANS FOR REPRODUCING SOUND FROM GRAPHICAL RECORDS Filed Aug. 15, 1923 Inve 71/2501"; .Russell Hart,

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\ electric Patented Oct. 27,1925.

UNITED STATES RUSSELL HART, 01? L128 GELES, @ALHORNht-t. I

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Application filed August 13, 1923 Serial No. 657,260.

To all whom it may concern:

Be it known that l RUSSELL HART, citi? zen of the United tates, residing at Los Angeles, in the county of Los Angeles and State of California, have invented a new and useful Means for Reproducing Sound from Graphical Records, of which the fol lowing is a specification.

l have illustrated in the accompanying drawing and shall describe herewith a preferred form of my invention. 1 shall also specifically mention certain of itsmore important objects. I desire to have it understood however-thatvarious changes and adaptations may be made without departing from the essence of the invention which is not limited to the form disclosed except as set forth in the appended claims; and that objects other than those specifically mentioned are included within it's'scope and. will appear to those familiar with the; art in-- volved.

My invention relates to improvements in means for-the reproduction of graphically recorded sound, and particularly to photomeans for such reproduction. Among my more important objects are, first to provide a satisfactory method for utilizing a continuous hotographicsonnd record for sound repro uction'; second, to afford facilities for timing and synchronizing the reproduced sound so that it may be used by the methods of cinematography to. produce talking motion pictures; third 'to avoid the use of optical slits and surfaces of any kind in sliding contact with the record; and, fourth, to accomplish the above by means of relatively simple, inexpensiv and thoroughly dependable apparatus.

My objects are attained in the manner ilillfihliallhed in the accompanying drawing, in w 1c Figure 1 is a diagram illustrating the the line 4 -4 of Fig. 3,1ooking in the direction of the arrows;

F'gure 5 is an enlarged front elevation of a preferred form of photo-electric cell used in connection with in apparatus; and,

Figure 6 is a side e ovation of apreferred form of incandescent lamp which I usually loy as a light source.

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milar reference numerals refer to similar parts throughout the several views.

In an application filed Dec. 22, 1922, st rial No. 608,499; and another. application filed Apr. 9, 1923, Serial No. 630,870; I disclosed means for producing continuous sound records onphotographic films. Such records comprise an opaque area bounded on one side by a straight line corresponding to the axis of abscissze, and on the other side by a complex curve referred to that axis and corresponding to the-sound wave recorded. It is with'the reproduction of such records'especially that theTpresentinvention is concerned.

In the drawings 7 represents a motion picture film with a sound record'8 thereon.) The film is mounted on reels .9 and is driven "by sprockets 10 at a uniform speed in the manner common in the motion icture art. Between the sprockets the lm passes through 9. picture gate 11 and is given an intermittent motionfor picture purposes, as

by a claw, device 12. The fihn loops 13 permit of this being done without interfering with the continuous motion of the film between the sprockets and-the reels. An arc lamp is indicated at 14,21; condensinglens group at I 15,;and projecting lenses at 16., By meansof these, an themechanism previously described, a motion picture may be projected on, a screen in the usual manner. v

At any convenient point, where the film has a uniform motion, as between a sprocket and its corresponding reel, the sound gate 17 is inserted. -This constitutes one of the essential elements of my invention and comprises a fixed plate 18, having a are pressed inwardly from cover 19 by screw studs 23 and springs 24; the studs being hinged cover 19, and'two pairs of olished raised runners 20 and 21, between w ich the ners 20 are afiixedorhmade' integral with plate 19, while runners 21 are movable and.

slidable throughfholes in the cover 19. This arrangement permits the film to be' accurately positioned without danger of marring the pictures and sound record, these 'surfacesbein g spaced by the runners so as not to come in'contact with any part of the sound gate.- 4

Cover 19 is provided with a small rectan gular aperture 25 and there is a similar aperture 26 in the plate immediately behind it. The walls of the latter aperture are preferably polished to render them highly reflecting, and behind this aperture a suitable sensitive photo-electric cell 27 is removably mounted in any convenient manner as by the clips 28. j

Any desired type of photoelectric 'cell, or photo-ionic device, may beemployedat 27 provided it is capable of reacting stron ly' to minute light variations further that the speed at. which it reacts is sufiiciently great to properlyrespond to the requirements of the moving record used. Such cells have been developed and are known'in the art; The type-of photo-cell here shown comprises a very fine platinum grid 29 filled with selenium or other photo- -active material, on a glass cover plate 30,

, "terminal wires 32. A cup 33 containing anhydrous calcium chloride, or a similar substance, is cemented upon the back ofthe of maintaining the filament tension posed between the lamp means (not shown) are provided for focus:

throughout the range of its temperature variations. The filament thus is alwa s rectilinear. The tubular lamp 37, in w 'ch the filament is mounted, is supported by a clamp 38 adapted for adjusting the filament at the proper vertical angle in a plane parallel to film. An objective lens group 39 is inter-- and the film, and

' ing this lens group to cast a very sharp d curve.

magnified ima e of thefilament upon the sound record 0 the film. The rays of light fallin upon the sound record in the manner just escribed w'ill constitute. an exceedingly narrow transverse band and be variably eclipsed b the opacity of the record in conformity wit the instantaneous values of the ordinates of the sound The un-eclipsed rays will pass through the filmand fall upon the active surface of the photo-electric cell and proportionally vary its resistance. Consequently,

- and provi ed and connected by platinized strips 31 to theif a constant electro-motiv-e force is applied to the terminals of the cell, the current in the cell' circuit will 'be modulated in conformity to the sound record; This modulated current is then utilized for telephonic reproduction of the original sound.

There are various ways known to the art for amplifyin make it availa le for loud speaking devices. One method. of doing this is illustrated dia-' grammatically in Fig. 2," wherein standard electrical devices are conventionally shown. In this diagram a loud speaking instrument is indicated at 40.

Reference was made above to synchronizing the sound reproduction and the operation of a picture film so that the invention the modulated current to Y could be employed for producing talking ,motion pictures. Inasmuch as the motion pictures .are intermittently projected from. the film, and the sound record must be con tinuously reproduced, it is impractical to make use o f'thesame portion of the film for these two purposes simultaneously. The sound record therefore is placed upon the film a definite distance either in advance or behind the corresponding picture, and the sound gate is similarly located, so as to operate in synchronism with the projected pictures.

The purpose of polishing the interior surfaces of orifice 26 previously mentioned is of light rays, so far as this is possible. In this way the light that passes the sound record may be utilized to the fullest possible extent for producing the desired effect uponv the photo-electrlc cell. 4

I desire to point out particularly that the arrangement and construction of my apparatus makes it entirely unnecessary to employ an optical slit in contact with the to render them reflecting, and non-absorbent,

recorded film, and that the surface of the v record is not subjected to sliding contact in any portion of my device. There is no danger from abrasion from this source therefore, and the life of the film is great- Iy'dengthened in consequence.

also wish to call attention to the fact {that my invention requires a relatively small iamount of energy for sound reproducing Z purposes. This is important and advantageous for several reasons, in addition to the reduced cost of energy consumption. For instance the small energy re uirement permits of the use of a battery ior lighting the filament 34, and this in turn results in a perfectlysteady reproducing light and absolutely eliminates the effect of stray noise in the reproduction due to audiofrequency variations in the light source. The effect of alternating current hum is completely avoided in this manner. Again, the small energy requirement makes it practically impossible to overheat the film, and

the use of such devices as automatic light gates to prevent burning the film is 'superfiuous.

I claim as my invention: 4 L A paratus for sound reproduction comprising; a uniformly movable 'film .having a sound record thereon adapted for.

continuously interceptinfiflight rays in varying degrees; a tenuous. lumina'ble filament in tension; an intermediate. lens] adapted for focusing an image'of said filament upon said record transversely to its direction of motion; and means for transforming the light rays that pass through the record into sound waves. Q

, 2. Apparatus for sound reproduction comprising; a uniformly movable film having a'sound record thereon adapted for.con-- tinuously intercepting. light rays in vary-- ing degrees; a linear light source. of great tenuity; an intermediate lens adapted ..for focusing an image of said source upon said record; means for angularly. adjusting-the position of said'image with respect to said record; and" means for transforming the,

.cularly u on said record; means for an? gularly a justing the position of said image with respect to the direction of motion of said record; a photo-electric cell behind modulating an electric current proportionally toflthe' amount of light that passes through the record; and means for utilizing said modulated current for the reproduction of sound.

4. In apparatus of the character de-; scribed, in combination, a photo-electric cell;

a spaced. opticalfilm; and an. intermediate aperture having highly reflectin walls.

RUSSELL 1 RT.

said record adjacent thereto adapted for 

